"Capsicum spray was used by our members on the front line and it was used at the time that the members were being trampled by union members and in fear of their safety," he said.

Police later left the site but around 50 union members remained, vowing to continue their protest.

The union has been blockading the Grocon site since last Wednesday.

Last week Grocon obtained a Supreme Court injunction banning some union figures from being at the site.

The court extended the order this afternoon.

Grocon claims the industrial action is costing the company more than $370,000 a day.

The court has ordered the union to stop preventing workers coming or going from the Emporium site and two others.

The CFMEU was not in court to oppose the ruling and has been given 48 hours to show that it has complied.

The court has also been told that a senior union official, John Setka, drove his car at a security guard outside a Grocon construction site in Footscray this morning.

Grocon manager Brian McAdam said that when the guard told Mr Setka he was breaching court orders by approaching the site, Mr Setka abused him and drove his car into the man's leg.

Grocon says the matter has been referred to the police.

The court heard that Mr Setka had abused several Grocon workers near the CBD picket.

Commander Nugent says police were trying to help the workers get on site.

"The dispute is not between the employees of Grocon, the dispute is union members over a separate issue. So it's not actually an industrial dispute over wages or conditions by the employees of Grocon.

"So therefore the union members are there illegally blockading entry to the worksite," he said.

Victorian CFMEU secretary Bill Oliver says Grocon has banned union insignia from the worksite and it will not let the unionists elect their own shop stewards or safety officers.

He defended the actions of the workers who attacked the police horses.

On this particular occasion, the law is wrong.

CFMEU state secretary Bill Oliver

"If a horse was coming to you at full pace, you've got to put your hands up to defend yourself and to fend them off," he said.

"I think that's exactly what's taken place this morning. There was no confrontation here by construction workers, they were pushing horses back, because those horses were trying to go and trample them down."

Mr Oliver accused Grocon and the State Government of provoking the clashes, while Grocon head Daniel Grollo accused the union of mounting an "illegal blockade".

"This is what he wants for every Victorian construction worker - violence and thuggery on building sites.

"We have been down here for seven days, it's been a peaceful demonstration, and not once has Grocon tried to enter this site," he said.

"There's no doubt that this was a stunt all organised by Daniel Grollo, organised by the State Government, to take on construction workers.

"This dispute is about construction workers [being] allowed to go to their job safely, not to go onto construction sites and be stood over every day of the week.

"This is a blockade just standing up for your rights. The way Grocon is treating construction workers, in this industry and on this site, he's trying to use the law. Well on this particular occasion, the law is wrong," he said.

But Mr Grollo said the union was acting outside the law by "defying" the Supreme Court.

"We sought the assistance of the Supreme Court. They've made orders. The union has defied those orders and seen themselves as being above the Supreme Court of Victoria," he said.

"This morning we sought the assistance of police to help us return those workers back work safely.

"It's not a picket line. It is an illegal blockade. It's an important point, because it's not an industrial issue here. Grocon has an EBA signed off three months ago, which Grocon employees and the union are party to. It's not about the terms and conditions of employment," he said.

"I think the Victorian leadership of the CFMEU this morning showed, and has shown themselves for the past week, they see themselves above the law in Victoria. I can't trust them while they're doing that. I can't trust them while they're intimidating and making death threats to workers.

"I think what we saw today is absolute disregard for the law and intimidation and bullying," he said.

Premier Ted Baillieu has condemned the protest.

"This is appalling behaviour. This is an illegal blockade, it's been declared so by the Supreme Court, and the people who are blockading have an obligation to obey the law and the police that are present have an obligation to uphold the law."

Mr Baillieu says the confrontation is an example of "union thuggery", which has been allowed to flourish since the Australian Building and Construction Commission (ABCC) was abolished.

"The Federal Government has a very clear position. We do not condone in any shape or form, regardless of who's doing it, unlawful action," he said.

"Confrontation never fixes arguments ultimately, and that it will involve talking at some point. Grocon has a very strong view about what's happening here and they are taking that to court.

"They're exercising their legal rights under a system that has been in place for a very long time.

"I am more than prepared to try and convince people of a better path. Would I have liked everyone to have agreed with me yesterday? Yup. But they haven't. But I'm not going to give up trying to resolve this matter with the tools I have," he said.

The Federal Opposition says the clash shows the need to reinstate the ABCC.